A wet spinning apparatus is an apparatus for solidifying a spinning raw liquid prepared by dissolution of an organic polymer in a solvent into a fiber form by discharging the spinning raw liquid from a nozzle into a coagulation liquid. Acrylic fibers, polyvinyl fibers, and other acrylic based fibers can be produced by the wet spinning apparatus.
The wet spinning apparatus is generally equipped with a spinning bath in which a coagulation liquid is contained, a nozzle immersed at one end in the spinning bath, and a drawing roll immersed at the other end in the spinning bath, wherein a spinning raw liquid discharged from the nozzle is coagulated by the coagulation liquid and thus formed into coagulated filaments which are then drawn out of the spinning bath through the drawing roll. The coagulation liquid is discharged into the spinning bath from a coagulation liquid discharge port disposed on the rear surface side of the nozzle, and is caused to flow to a running direction of the coagulated filaments while coagulating the coagulated filaments, and is caused to flow out into a coagulation liquid recovery portion from a spinning bath outlet port disposed at the other end in the spinning bath. Fibers (coagulated filaments) solidified in the spinning bath are separated from the coagulation liquid, washed, and transferred to the subsequent steps such as chemical liquid treatment, drying, and thermal treatment.
The speed of spinning and drawing of the coagulated filaments is generally set faster than the average flow rate of the coagulation liquid to be supplied into the spinning bath. As a result, the coagulation liquid flowing in the vicinity of the coagulated filaments is attracted by and accompanies the coagulated filaments, and is caused to flow to the direction of drawing with a velocity near a spinning speed (hereinafter, this is referred to as “accompanying flow”). At the same time, there occurs a phenomenon such that the coagulation liquid flows backward from the downstream side to the upstream side to compensate the accompanying flow at a place near the bottom wall or the sidewall which is distant from the coagulated filaments in the spinning bath. In this way, there have been simultaneously and adjacently generated two flows contrary to each other, namely the accompanying flow and the counter flow, in the spinning bath, so that the flows have interfered each other to cause irregular flow of the coagulation liquid and thus there have been partially generated whirlpools and stagnation.
When such whirlpools and stagnation were generated in the spinning bath, there was a case where filament waste (nest) derived from break of a single fiber caused by poor coagulation of the spinning raw liquid floated in the spinning bath and lumps of the filament waste came into contact with the coagulated filaments and thereby deterioration of quality and performance of the product was caused. In addition, when the spinning speed was raised to improve productivity, stable production was disturbed because turbulent flow of the coagulation liquid became more remarkable and the coagulated filaments were shaken and thus diameter-unevenness or break of a single fiber was generated.
Therefore, the following wet spinning apparatus has been proposed to solve the above-mentioned problem.
A wet spinning apparatus equipped with rectifying plates provided on both sides of the coagulated filaments along with the running direction of the coagulated filaments (for example, Patent Document 1). As for this wet spinning apparatus, turbulence of the flow of the coagulation liquid can be suppressed by the rectifying plates.
However, as for such a wet spinning apparatus, there was a case where the flow rate of the coagulation liquid at a part where the coagulation liquid flowed out from the spinning bath became too fast and thus turbulence of the coagulated filaments (tow) was caused.
Accordingly, there has been proposed a wet spinning apparatus in which a coagulation liquid-partitioning plates (rectifying plates) for partitioning the coagulation liquid are provided between the coagulated filaments and walls of the spinning bath standing in parallel with the running direction of the coagulated filaments, and holes (openings) for drawing out coagulation liquid are formed on the coagulation liquid-partitioning plates (for example, Patent Documents 2 to 4). As for this wet spinning apparatus, the inside of the spinning bath is separated into an inner bath which is located inside the coagulation liquid-partitioning plates and in which the coagulated filaments are running, and outer baths located on both sides of the inner bath; the accompanying flow generated in the spinning bath is allowed to flow inside the inner bath toward downstream side, and the counter flow is allowed to flow inside the outer baths toward upstream side. In addition, it is possible to restrain the flow rate of the coagulation liquid from being too fast by causing the coagulation liquid to flow out from the inner bath to the outer baths through the openings.    Patent Document 1: Japanese Patent Application Laid-Open No. Sho 62-33,814    Patent Document 2: Japanese Patent Application Laid-Open No. Hei 9-67,714    Patent Document 3: Japanese Examined Utility Model Publication No. Sho 41-18,091    Patent Document 4: Japanese Patent Application Laid-Open No. Hei 11-229,227